The current goals of this project are an examination of the conductance mechanisms found in nerve cell bodies. The particular conductance mechanism currently under study is the inwardly rectifying K ion conductance or "anomolous rectifier." This system is unique among K ion conductance pathways in that the conductance to ions other than K ion is extremely low; i.e., P K/P Rb is approximately equal to 20. This contrasts with other K ion conducting systems in this membrane whose P K to P Rb ratios are close to 1. Additionally the Q 10 at this conductance is high, of the order of 3.4. The permeability sequence is K much greater than Rb greater than Cs greater than Na equals Li. The system is also unusual in that the conductance is not only voltage dependent but also dependent upon the driving force for potassium ion. To study the effect internal potassium ion will be varied by using the antibiotic nystatin. This dependence of the conductance on both voltage and driving force makes the current through this pathway a complicated function of external and internal K ion and voltage. A model is being developed to simulate the system. BIBLIOGRAPHIC REFERENCES: Eaton, D.C., and Brodwick M.S. Inward Rectification in Aplysia Giant Neurons. Biophys. J. 16:124a, 1976. (Abstract) Russell, J.M., Eaton, D.C., and Brodwick M.S. Effects of Nystatin on the Aplysia Giant Neuron. Biophys. J. 16:75a, l976. (Abstract)